1. Field of the Invention
This invention relates generally to a spring-mass-support structure in which the mass is supported by springs where displacement of the spring supported mass may be sensed electrostatically or by other means to provide a signal proportional to a characteristic of motion such as position, velocity or acceleration applied to the support structure.
2. Description of the Prior Art
Heretofore, silicon accelerometers or sensing devices have been constructed with a spring supported mass in a support structure. For example, U.S. Pat. No. 4,922,756 dated May 8, 1990 to Henrion shows a silicon acceterometer in which a spring-mass-support sensing structure has a sensing mass supported from a support frame by a plurality of E-shaped leaf springs formed of silicon dioxide. Each of the leaf springs includes a base with two integral outer legs and an integral inner leg connected to the base. The inner leg is connected to the mass while the outer legs are connected to the support frame. Displacement of the mass applied to the support structure is measured by suitable electronic circuitry which may be arranged to provide an analog or binary representation of the acceleration or velocity applied to the support structure or of the position of such support structure.
U.S. Pat. No. 4,144,516 to Aine dated Mar. 13, 1979 discloses a dual leaf spring transducer in which a pair of E-shaped leaf springs are connected between a central mass and an outer support structure. The E-shaped leaf springs are mounted in mutually opposed relation so that the leaf spring structures are coupled together for deflection in unison relative to the surrounding support structures in response to deflection of the mass with respect to the support structure. A capacitive detector device is provided for detecting displacement of the mass.
U.S. Pat. No. 4,553,436 dated Nov. 19, 1985 to Hansson discloses a silicon accelerometer in which a central mass is connected at its corners by four thin, flexible spring legs secured to an outer support structure. The legs extend in a single direction parallel to the mass. Each leg has an end connected at right angles to a side of the mass adjacent a corner. The stationary ends of the legs or springs are connected to the support frame.
U.S. Pat. No. 4,641,539 dated Feb. 10, 1987 to Vilimek shows a mass (called a force takeup element) connected by four spring support legs to the support structure. The support legs extend in a direction parallel to the adjacent edge of the mass and have one end connected to the adjacent edge adjacent a corner of the mass. The other stationary end of each leg is connected to the support structure or body. The legs are thin leaf-spring like strips which deform upon displacement of the mass. The displacement of the mass is measured in a well known manner.
It is desired that spring members disposed between a mass and its adjacent support structure be highly insensitive to shock forces or impacts in directions orthogonal to the measurement axis of the mass and support structure and not buckle when lateral forces are applied to such support structure. However, many of the prior art frame-spring-mass configurations do not provide sufficient insensitivity to acceleration or angular motion which are in the plane of the mass, and the springs of such prior art configurations tend to buckle in response to lateral forces. Furthermore, it is desired that a frame-spring-mass system be extremely linear in its measurement of acceleration and be characterized by minimum stress on its springs where force is applied along its measurement axis. Many prior art frame-spring-mass designs do not provide sufficient linearity or minimization of spring stress in response to force applied to the measurement